Pasty silver particle composition, process for producing solid silver, solid silver, joining method, and process for producing printed wiring board

Abstract

To provide a pasty silver particle composition, which, upon heating, allows silver particles to be easily sintered to form solid silver possessing excellent strength, electric conductivity and thermal conductivity, and a production process of solid silver and the like. A pasty silver particle composition comprising nonspherical silver particles having an average particle diameter of 0.1 to 18 μm and a carbon content of not more than 1.0% by weight and a volatile dispersion medium, wherein, upon heating, the volatile dispersion medium is volatilized and the nonspherical silver particles are sintered to one another to form solid silver. There are also provided a process for producing solid silver comprising heating the pasty silver particle composition, solid silver having excellent strength, electric conductivity and thermal conductivity, a method for joining a metallic member using the pasty silver particle composition, and a production process of a printed wiring board comprising silver wiring.

1. A pasty silver particle composition, characterized by comprising (A) non-spherical silver particles having an average particle diameter of 0.1 to 18 μm, a surface at least partially coated with a higher fatty acid or its derivative, and wherein the coated particles have a non-zero carbon content of 1.0 weight % or less, wherein the ratio of silver oxide on the surface of the silver particles to silver particle surface area is less than 50%; and (B) a volatile dispersion medium having a boiling point from 100° C. to 400° C. in an amount sufficient to make the non-spherical silver particles of (A) pasty, selected from: water; a volatile monohydric alcohol selected from the group consisting of ethyl alcohol, propyl alcohol, butyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, and benzyl alcohol; an ether; aliphatic carboxylic acid ester; or aliphatic hydrocarbon solvent. 
     
     
       2. The pasty silver particle composition according to  claim 1 , characterized in that the non-spherical silver particles are flake-like silver particles or granular silver particles. 
     
     
       3. A process for producing solid silver, characterized by comprising heating the pasty silver particle composition according to  claim 1  at 100° C. or higher and 400° C. or lower, whereby the volatile dispersion medium is volatilized and the silver particles are sintered. 
     
     
       4. Solid silver characterized in that solid silver produced by the producing process according to  claim 3  has a volume resistivity of 1×10 −5  Ω·cm or less and a thermal conductivity of 10 W/m·K or more. 
     
     
       5. A joining method characterized by comprising interposing the pasty silver particle composition according to  claim 1  between a plurality of metal members and heating at 100° C. or higher and 400° C. or lower, whereby the volatile dispersion medium is volatilized and the silver particles are sintered to join the plurality of metal members. 
     
     
       6. The joining method according to  claim 5 , characterized in that the plurality of metal members are a metal substrate or an electrode on an electrically insulating substrate, and a metal portion of an electronic component or an electrical component. 
     
     
       7. A process for producing a printed wiring board, characterized by comprising applying the pasty silver particle composition comprising (A) non-spherical silver particles having an average particle diameter of 0.1 to 18 μm, a surface at least partially coated with a higher fatty acid or its derivative, and a carbon content of 1.0 weight % or less and (B) a volatile dispersion medium on a substrate, to which an adhesive is applied, and heating at 100° C. or higher and 400° C. or lower before the adhesive is cured, whereby the volatile dispersion medium is volatilized and the silver particles are sintered and simultaneously the adhesive is cured to form silver wiring. 
     
     
       8. The pasty silver particle composition according to  claim 1 , characterized in that the amount of the volatile dispersion medium (B) is 5 to 20 parts by weight per 100 parts by weight of the non-spherical silver particles (A). 
     
     
       9. The process of  claim 7 , wherein the volatile dispersion medium has a boiling point between 100° C. and 400° C. 
     
     
       10. The past silver composition of  claim 1 , wherein the ratio of silver oxide on the surface of the silver particles to silver particle surface area is less than 20%. 
     
     
       11. The past silver composition of  claim 1 , wherein the ratio of silver oxide on the surface of the silver particles to silver particle surface area is less than 2%.